Vehicles include various sensors and electronic control units (ECUs) that monitor and control subsystems of the vehicle. For example, a body control module controls door locks, windows, mirrors, lights, and horn of the vehicle. The ECUs communicate and exchange information via a vehicle data bus. The information may include status data, sensor readings, diagnostic codes, and requests to perform actions or enter diagnostic modes. However, malicious actors may install unauthorized devices on the vehicle data bus (e.g., via the on-board diagnostic port (OBD-II)) to monitor and control the subsystems of the vehicle.